The present invention is directed to a method for the preparation of promoted VSbOx based catalyst useful in the catalytic vapor phase ammoxidation of propylene or isobutylene to acrylonitrile or methacrylonitrile. In addition, the present invention is directed to a method for catalytic vapor phase ammoxidation of propylene or isobutylene to acrylonitrile or methacrylonitrile in a fluid bed reactor by contacting with a fluid bed ammoxidation catalyst made by the process of the present invention.
U.S. Pat. No. 4,162,992 discloses the ammoxidation of olefins, especially propylene, using a catalyst containing vanadium, antimony and titanium. However, the amount of antimony is far outside the range of the catalyst made by the present claimed process.
In U.S. Pat. No. 3,681,421 to Barclay et al there is disclosed the vapor phase catalytic ammoxidation of propylene over an oxide composition comprising antimony, vanadium and one or more additional poly-valent metals selected from the group of tin, iron, cobalt and titanium. The catalyst disclosed by Barclay et al overlap with the empirical formula of the compositions of the catalyst of the present invention. However, the catalyst of the present invention are made by a different method than the catalyst disclosed by Barclay et al.
Finally, in U.S. Pat. No. 5,258,543 to Suresh et al, assigned to the assignee of the instant application, there is disclosed a suitable procedure for making a VSbOx promoted catalyst useful in the ammoxidation of propylene to acrylonitrile. The present invention is directed to an improvement in the procedure for making the VSbOx promoted catalyst of the U.S. Pat. No. 5,258,543. The properties of the catalyst prepared by the present invention have superior properties than those disclosed in the prior art.
It is the primary object of the present invention to provide a novel process for the preparation of promoted VSbOx based catalyst useful in the ammoxidation of propylene or isobutylene to produce acrylonitrile or methacrylonitrile.
It is another object of the present invention to provide a novel procedure for the catalytic vapor phase ammoxidation of propylene or propane to acrylonitrile or methacrylonitrile.
Additional objects, advantages and novel features of the invention, will be set forth in part in the description which follows, and, in part, will become apparent to those skilled in the art upon examination of the following or may be learned by the practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the foregoing and other objects and in accordance with the purpose of the present invention as embodied and broadly described herein, the process of the present invention comprises preparing a supported catalyst wherein said catalyst comprises the elements and proportions indicated by the following empirical formula:
V1.0SbaMbOx
wherein
M equals Sn, Ti, Fe, Cu, Nb, Ta, Co, Ni, Mg, Li, Na, Ga and mixtures thereof,
a is from about 0.5 to about 5.0,
b is from about 0.1 to 5.0, and
x is the number of oxygen atoms required to satisfy the valency requirement of the other elements,
comprising (1) mixing the vanadium compound, at least a portion of the antimony compound, at least a portion of the M compound and an aqueous sol containing a portion of the support material to form an aqueous slurry, heating the slurry to remove the water, and calcining at a temperature of at least about 150xc2x0 C. to form a catalyst precursor; (2) mixing the catalyst precursor with an aqueous sol containing the remaining portion of the support material and any remaining portion of the antimony and M compounds to form a second slurry, (3) drying the second slurry to remove the water to form a dry mixture, and (4) calcining the dried mixture at a temperature of at least 150xc2x0 C. to form the finished catalyst.
In a preferred embodiment of the present invention the portion of the support material added during the formation of the catalyst precursor is between 1 to 79% of the total amount of support material present in the finished catalyst.
In a further preferred embodiment of the present invention the remaining portion of support material present in the aqueous sol to which the catalyst precursor is mixed is between 1 to 79% of the total amount of support material present in the finished catalyst.
In still another preferred embodiment of the present invention all of the antimony compound is added during the formation of the catalyst precursor.
In still a further preferred embodiment of the present invention all of the M compound is added during the formation of the catalyst precursor.
In another further preferred embodiment of the present invention the catalyst precursor is calcined at a temperature of between about 150xc2x0 to about 900xc2x0 C., preferably between about 250xc2x0 to 800xc2x0 C., especially preferred being between about 300xc2x0 to about 600xc2x0 C.
In another preferred embodiment of the present invention the support material is selected from the group consisting of silica, alumina, titanium, zirconia, and mixtures thereof.
In a still further preferred embodiment of the present invention, the process further comprises forming the first aqueous slurry by mixing an aqueous dispersion containing the vanadium compound and at least a portion of the antimony compound while the vanadium is in solution prior to calcining to form the catalyst precursor.
In accordance with additional aspects of the present invention as embodied and broadly described herein, the method of manufacture of acrylonitrile or methacrylonitrile from propylene or isobutylene comprises introducing in the vapor state a hydrocarbon selected from the group consisting of propylene and propane, an oxygen-containing gas and ammonia into a fluid bed reactor containing an ammoxidation catalyst, wherein the catalyst contains elements in proportions indicated in the empirical formula set forth above. Wherein the catalyst is prepared by a process comprising (1) mixing the vanadium compounds, at least a portion of the antimony compound, at least a portion of the M compound and an aqueous sol containing a portion of the support material to form an aqueous slurry, heating the slurry to remove the water, and calcining at a temperature of at least about 150xc2x0 C. to form a catalyst precursor; (2) mixing the catalyst precursor with an aqueous sol containing the remaining portion of the catalyst and any remaining portion of the antimony and M compounds to form a second slurry, (3) drying the second slurry to remove the water to form a dry mixture, and (4) calcining the dried mixture at a temperature of at least 150xc2x0 C. to form the finished catalyst.
In a preferred embodiment of this aspect of the present invention the olefin is selected to be propylene.
In a still further preferred embodiment of this aspect of the present invention the olefin is selected to be isobutylene.
The present invention is directed to a method of preparing a supported catalyst useful in the ammoxidation of acrylonitrile or methacrylonitrile. The catalyst comprises the elements in proportions indicated by the following empirical formula:
V1.0SbaMbOx
wherein
M equals Sn, Ti, Fe, Cu, Nb, Ta, Co, Ni, Mg, Li, Na, Ga and mixtures thereof,
a is from about 0.5 to about 5.0,
b is from about 0.1 to 5.0, and
x is the number of oxygen atoms required to satisfy the valency requirement of the other elements.
The process of preparing the above-identified catalyst comprises mixing the vanadium compound, at least a portion of the antimony compound, at least a portion of the M compound in an aqueous sol containing a portion of the support material to form an aqueous slurry, heating the slurry to remove the water and calcining in a temperature of at least about 150xc2x0 C. to form a catalyst precursor; (2) mixing the catalyst precursor with aqueous sol containing the remaining portion of the support for the catalyst and any remaining portion of the antimony and M compounds to form a second slurry; (3) drying the second slurry to remove the water to form a dry mixture, and calcining the dried mixture at a temperature of at least 150xc2x0 C. to form the finished catalyst.
In particular, the catalyst precursor is made by the process disclosed in U.S. Pat. No. 5,258,543 assigned to the assignee of the present invention and herein incorporated by reference. In general, the catalyst precursor comprising vanadium antimony promoted oxide is made by adding the vanadium pentoxide to water containing hydrogen peroxide and stirring until a dark red peroxide complex has been formed. At least a portion of the antimony compound, preferably all the antimony compound, is then added to the slurry and the slurry is heated with the color in the slurry generally changing from yellow to green to black. The mixture is digested for approximately 3 hours while adding water to keep the volume constant. At least a portion of the M compound is added in the form of the water soluble salt, e.g. (metal salt) followed by the addition of at least a portion of the support material in the form of aqueous sol. The slurry is then evaporated on a hot plate at approximately a temperature of 120xc2x0 C. and then calcined at a temperature of at least 150xc2x0 C., preferably between 600xc2x0 to 900xc2x0 C., most preferably above 750xc2x0 C. to form the catalyst precursor. For details with regard to the formation of the catalyst precursor, reference is made to U.S. Pat. No. 5,258,543 assigned to the assignee of the present invention and herein incorporated by reference.
The catalyst precursor made by the above procedure is then added to an aqueous sol containing the remaining portion of the support for the catalyst and any remaining portion of the antimony and M compounds. Typically, the antimony compound in the form of antimony oxide or the M compound in the form of a metal salt is simply mixed with the aqueous sol containing the remaining portion of the support for the catalyst prior to mixing with the catalyst precursor.
In the preferred embodiments of the present invention, Support material is selected from the group consisting of silica, alumina titanium, zirconium, and mixtures thereof. It is especially preferred that an aqueous sol of silica be used. Typical sources of silica useful in the practice of the present invention can be obtained from the Nalco Chemical Company of Chicago, Ill.
The catalyst prepared by the process of the present invention has particular utility in the ammoxidation of propylene and isobutylene to the corresponding xcex1,xcex2 mono-unsaturated nitrile. The process comprises introducing the hydrocarbon, an oxygen-containing gas and ammonia into a reactor containing the ammoxidation catalyst prepared by the procedure of the present invention wherein the catalyst contains the elements in proportions indicated in the empirical formula set forth below:
V1.0SbaMbOx
wherein
M equals Sn, Ti, Fe, Cu, Nb, Ta, Co, Ni, Mg, Li, Na, Ga and mixtures thereof,
a is from about 0.5 to about 5.0,
b is from about 0.1 to 5.0, and
x is the number of oxygen atoms required to satisfy the valency requirement of the other elements.
Typically, the ammoxidation reaction is carried out in the temperature ranging from 350xc2x0 to 700xc2x0 C., preferably in the range of 430xc2x0 to 520xc2x0 C. Moreover, the reaction is carried out in the gaseous phase by contacting the mixture of the olefin, ammonia, molecular oxygen (oxygen containing gas) and an inert diluent, if any, in either a fixed bed, fluid bed, or fast transport reactor. In the preferred embodiment of the present invention, a fluid bed reactor is used.
Examples of applicable inert gaseous diluents are nitrogen, helium, carbon dioxide and water. In the process of the present invention the volume ratio of inert gaseous diluents to olefin fed to the reaction zone is usually in the range of 0 to 8, more often 0 to 4.
The average contact time can be from 0.01 to 10 seconds but is usually from 0.02 to 5 seconds, especially preferred being 0.1 to 2 seconds.
The pressure in the reaction zone usually ranges from just over atmospheric to up to 75 atmospheres, especially preferred being up to 50 psia.
The catalyst prepared by the process of the present invention similarly to the catalyst prepared in U.S. Pat. No. 5,258,543 have outstanding characteristics as propylene ammoxidation catalysts with acrylonitrile yields similar to those obtained with present day commercial amtimonate catalysts. The promoted catalysts of the present invention have significant potential as high throughput catalysts which give low levels of waste organics during use. A significant advantage of the catalyst prepared by the process of the present invention is that the process of the present invention allows for significantly easier preparation of the catalyst, along with increasing the hardness of the catalyst, which will result in additional or improved attrition resistance when used in the fluid bed reactor.